Several compounds are being synthesized which are expected to have the property of forming covalent bonds with acetylcholine receptors. Two such drugs have been subjected to preliminary in vitro testing. Experiments using activity monitoring techniques indicate that the drugs are anticholinergic when applied to schistosomes in vitro. In addition, a one-hour drug exposure followed by overnight incubation in drug-free medium appears to result in irreversible damage to the worms. Studies were also conducted of fluourescence induced in schistosomes by DDNS, a fluorescence acetylcholine analog. Results indicate cholinergic binding activity by this method as well. Finally, experiments with vertebrate muscle preparations show that the drugs have cholinomimetic activity in muscarinic systems, but that the relative activity of the two tested drugs was reversed in the vertebrate, as compared to the schistosome preparations. Future work will extend the structure-activity series and extend the methodology to small scale in vivo tests.